The present application is based on and claims priority from Japanese Patent Application 2000-198257, filed Jun. 30, 2000, the contents of which are incorporated herein by reference.
1. Field of the Invention
The present invention relates to a vehicle rotary electric machine and, particularly, an AC generator to be mounted on an engine.
2. Description of the Related Art
JP-A-2-414650 and JP-A-10-248191 disclose a side-mounting type AC generator that includes a pulley and a housing having a plurality of bolt-holes extending in a direction perpendicular to a shaft of the generator. Usually, such bolt-holes have a diameter that is much larger than the diameter of bolts so that the bolt-holes can absorb dispersion in positions of the female threads that are formed at an engine so that the generator can be easily mounted on the engine. In the meanwhile, it is very difficult to accurately position the cylinder head of the engine on the cylinder block thereof because both members are fastened by bolts to each other via a gasket.
As the diameter of the bolt-holes becomes larger, it becomes more difficult to locate the pulley of the AC generator at a proper position. If the pulley is not positioned properly, the friction loss of the belt may increase and the lifetime thereof may decrease. Therefore, it has been recommended that the bolt-holes are formed by a machine to provide an accurate diameter.
Therefore, a main object of the invention is to provide a pulley-driven vehicle rotary electric machine that has an improved bolt-fastening structure.
Another object of the invention is to provide a pulley-driven vehicle rotary electric machine that is easy to mount on an engine at a proper position where the friction loss o the belt may not increase.
In a vehicle rotary electric machine according to a feature of the invention, a housing has an elliptical first bolt-hole extending in a direction perpendicular to a shaft at a position outside an axial end of the housing and a circular second bolt-hole disposed at the opposite position with respect to the shaft to extend approximately in the same direction as the first bolt-hole. The elliptic second bolt-hole has a major axis approximately extending in a direction perpendicular to the shaft and a minor axis extending in the direction parallel to the shaft. The major axis may extend in a direction between xe2x88x9210xc2x0 and 10xc2x0 from said direction perpendicular to said shaft. The housing may have a circular third bolt-hole that is larger than the minor axis of the first bolt hole disposed at the same radial position as the second bolt-hole extending in parallel with the first bolt-hole.